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|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/commands/run_aggregate.h"
#include <boost/optional.hpp>
#include <memory>
#include <vector>
#include "mongo/db/api_parameters.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/catalog/collection_uuid_mismatch.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/commands/cqf/cqf_aggregate.h"
#include "mongo/db/curop.h"
#include "mongo/db/cursor_manager.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/exec/disk_use_options_gen.h"
#include "mongo/db/exec/document_value/document.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/fle_crud.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/pipeline/aggregation_request_helper.h"
#include "mongo/db/pipeline/change_stream_invalidation_info.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_exchange.h"
#include "mongo/db/pipeline/document_source_geo_near.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/pipeline.h"
#include "mongo/db/pipeline/pipeline_d.h"
#include "mongo/db/pipeline/plan_executor_pipeline.h"
#include "mongo/db/pipeline/process_interface/mongo_process_interface.h"
#include "mongo/db/pipeline/search_helper.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/query/collection_query_info.h"
#include "mongo/db/query/cursor_response.h"
#include "mongo/db/query/find_common.h"
#include "mongo/db/query/get_executor.h"
#include "mongo/db/query/plan_executor_factory.h"
#include "mongo/db/query/plan_summary_stats.h"
#include "mongo/db/query/query_feature_flags_gen.h"
#include "mongo/db/query/query_knobs_gen.h"
#include "mongo/db/query/query_planner_common.h"
#include "mongo/db/read_concern.h"
#include "mongo/db/repl/oplog.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/db/repl/speculative_majority_read_info.h"
#include "mongo/db/s/collection_sharding_state.h"
#include "mongo/db/s/operation_sharding_state.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/db/service_context.h"
#include "mongo/db/stats/resource_consumption_metrics.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/db/views/view.h"
#include "mongo/db/views/view_catalog_helpers.h"
#include "mongo/logv2/log.h"
#include "mongo/util/scopeguard.h"
#include "mongo/util/string_map.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand
namespace mongo {
using boost::intrusive_ptr;
using std::shared_ptr;
using std::string;
using std::stringstream;
using std::unique_ptr;
Counter64 allowDiskUseFalseCounter;
namespace {
ServerStatusMetricField<Counter64> allowDiskUseMetric{"query.allowDiskUseFalse",
&allowDiskUseFalseCounter};
/**
* If a pipeline is empty (assuming that a $cursor stage hasn't been created yet), it could mean
* that we were able to absorb all pipeline stages and pull them into a single PlanExecutor. So,
* instead of creating a whole pipeline to do nothing more than forward the results of its cursor
* document source, we can optimize away the entire pipeline and answer the request using the query
* engine only. This function checks if such optimization is possible.
*/
bool canOptimizeAwayPipeline(const Pipeline* pipeline,
const PlanExecutor* exec,
const AggregateCommandRequest& request,
bool hasGeoNearStage,
bool hasChangeStreamStage) {
return pipeline && exec && !hasGeoNearStage && !hasChangeStreamStage &&
pipeline->getSources().empty() &&
// For exchange we will create a number of pipelines consisting of a single
// DocumentSourceExchange stage, so cannot not optimize it away.
!request.getExchange();
}
/**
* Returns true if we need to keep a ClientCursor saved for this pipeline (for future getMore
* requests). Otherwise, returns false. The passed 'nsForCursor' is only used to determine the
* namespace used in the returned cursor, which will be registered with the global cursor manager,
* and thus will be different from that in 'request'.
*/
bool handleCursorCommand(OperationContext* opCtx,
boost::intrusive_ptr<ExpressionContext> expCtx,
const NamespaceString& nsForCursor,
std::vector<ClientCursor*> cursors,
const AggregateCommandRequest& request,
const BSONObj& cmdObj,
rpc::ReplyBuilderInterface* result) {
invariant(!cursors.empty());
long long batchSize =
request.getCursor().getBatchSize().value_or(aggregation_request_helper::kDefaultBatchSize);
if (cursors.size() > 1) {
uassert(
ErrorCodes::BadValue, "the exchange initial batch size must be zero", batchSize == 0);
BSONArrayBuilder cursorsBuilder;
for (size_t idx = 0; idx < cursors.size(); ++idx) {
invariant(cursors[idx]);
BSONObjBuilder cursorResult;
appendCursorResponseObject(cursors[idx]->cursorid(),
nsForCursor.ns(),
BSONArray(),
cursors[idx]->getExecutor()->getExecutorType(),
&cursorResult);
cursorResult.appendBool("ok", 1);
cursorsBuilder.append(cursorResult.obj());
// If a time limit was set on the pipeline, remaining time is "rolled over" to the
// cursor (for use by future getmore ops).
cursors[idx]->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
// Cursor needs to be in a saved state while we yield locks for getmore. State
// will be restored in getMore().
cursors[idx]->getExecutor()->saveState();
cursors[idx]->getExecutor()->detachFromOperationContext();
}
auto bodyBuilder = result->getBodyBuilder();
bodyBuilder.appendArray("cursors", cursorsBuilder.obj());
return true;
}
CursorResponseBuilder::Options options;
options.isInitialResponse = true;
if (!opCtx->inMultiDocumentTransaction()) {
options.atClusterTime = repl::ReadConcernArgs::get(opCtx).getArgsAtClusterTime();
}
CursorResponseBuilder responseBuilder(result, options);
auto curOp = CurOp::get(opCtx);
auto cursor = cursors[0];
invariant(cursor);
auto exec = cursor->getExecutor();
invariant(exec);
ResourceConsumption::DocumentUnitCounter docUnitsReturned;
bool stashedResult = false;
// We are careful to avoid ever calling 'getNext()' on the PlanExecutor when the batchSize is
// zero to avoid doing any query execution work.
for (int objCount = 0; objCount < batchSize; objCount++) {
PlanExecutor::ExecState state;
BSONObj nextDoc;
try {
state = exec->getNext(&nextDoc, nullptr);
} catch (const ExceptionFor<ErrorCodes::CloseChangeStream>&) {
// This exception is thrown when a $changeStream stage encounters an event that
// invalidates the cursor. We should close the cursor and return without error.
cursor = nullptr;
exec = nullptr;
break;
} catch (const ExceptionFor<ErrorCodes::ChangeStreamInvalidated>& ex) {
// This exception is thrown when a change-stream cursor is invalidated. Set the PBRT
// to the resume token of the invalidating event, and mark the cursor response as
// invalidated. We expect ExtraInfo to always be present for this exception.
const auto extraInfo = ex.extraInfo<ChangeStreamInvalidationInfo>();
tassert(5493701, "Missing ChangeStreamInvalidationInfo on exception", extraInfo);
responseBuilder.setPostBatchResumeToken(extraInfo->getInvalidateResumeToken());
responseBuilder.setInvalidated();
cursor = nullptr;
exec = nullptr;
break;
} catch (DBException& exception) {
auto&& explainer = exec->getPlanExplainer();
auto&& [stats, _] =
explainer.getWinningPlanStats(ExplainOptions::Verbosity::kExecStats);
LOGV2_WARNING(23799,
"Aggregate command executor error: {error}, stats: {stats}, cmd: {cmd}",
"Aggregate command executor error",
"error"_attr = exception.toStatus(),
"stats"_attr = redact(stats),
"cmd"_attr = cmdObj);
exception.addContext("PlanExecutor error during aggregation");
throw;
}
if (state == PlanExecutor::IS_EOF) {
// If this executor produces a postBatchResumeToken, add it to the cursor response. We
// call this on EOF because the PBRT may advance even when there are no further results.
responseBuilder.setPostBatchResumeToken(exec->getPostBatchResumeToken());
if (!cursor->isTailable()) {
// Make it an obvious error to use cursor or executor after this point.
cursor = nullptr;
exec = nullptr;
}
break;
}
invariant(state == PlanExecutor::ADVANCED);
// If adding this object will cause us to exceed the message size limit, then we stash it
// for later.
if (!FindCommon::haveSpaceForNext(nextDoc, objCount, responseBuilder.bytesUsed())) {
exec->stashResult(nextDoc);
stashedResult = true;
break;
}
// If this executor produces a postBatchResumeToken, add it to the cursor response.
responseBuilder.setPostBatchResumeToken(exec->getPostBatchResumeToken());
responseBuilder.append(nextDoc);
docUnitsReturned.observeOne(nextDoc.objsize());
}
if (cursor) {
invariant(cursor->getExecutor() == exec);
// For empty batches, or in the case where the final result was added to the batch rather
// than being stashed, we update the PBRT to ensure that it is the most recent available.
if (!stashedResult) {
responseBuilder.setPostBatchResumeToken(exec->getPostBatchResumeToken());
}
// If a time limit was set on the pipeline, remaining time is "rolled over" to the
// cursor (for use by future getmore ops).
cursor->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
curOp->debug().cursorid = cursor->cursorid();
// Cursor needs to be in a saved state while we yield locks for getmore. State
// will be restored in getMore().
exec->saveState();
exec->detachFromOperationContext();
} else {
curOp->debug().cursorExhausted = true;
}
const CursorId cursorId = cursor ? cursor->cursorid() : 0LL;
responseBuilder.done(cursorId, nsForCursor.ns());
auto& metricsCollector = ResourceConsumption::MetricsCollector::get(opCtx);
metricsCollector.incrementDocUnitsReturned(docUnitsReturned);
return static_cast<bool>(cursor);
}
StatusWith<StringMap<ExpressionContext::ResolvedNamespace>> resolveInvolvedNamespaces(
OperationContext* opCtx, const AggregateCommandRequest& request) {
const LiteParsedPipeline liteParsedPipeline(request);
const auto& pipelineInvolvedNamespaces = liteParsedPipeline.getInvolvedNamespaces();
// If there are no involved namespaces, return before attempting to take any locks. This is
// important for collectionless aggregations, which may be expected to run without locking.
if (pipelineInvolvedNamespaces.empty()) {
return {StringMap<ExpressionContext::ResolvedNamespace>()};
}
// Acquire a single const view of the CollectionCatalog and use it for all view and collection
// lookups and view definition resolutions that follow. This prevents the view definitions
// cached in 'resolvedNamespaces' from changing relative to those in the acquired ViewCatalog.
// The resolution of the view definitions below might lead into an endless cycle if any are
// allowed to change.
auto catalog = CollectionCatalog::get(opCtx);
std::deque<NamespaceString> involvedNamespacesQueue(pipelineInvolvedNamespaces.begin(),
pipelineInvolvedNamespaces.end());
StringMap<ExpressionContext::ResolvedNamespace> resolvedNamespaces;
while (!involvedNamespacesQueue.empty()) {
auto involvedNs = std::move(involvedNamespacesQueue.front());
involvedNamespacesQueue.pop_front();
if (resolvedNamespaces.find(involvedNs.coll()) != resolvedNamespaces.end()) {
continue;
}
// If 'ns' refers to a view namespace, then we resolve its definition.
auto resolveViewDefinition = [&](const NamespaceString& ns) -> Status {
auto resolvedView = view_catalog_helpers::resolveView(opCtx, catalog, ns, boost::none);
if (!resolvedView.isOK()) {
return resolvedView.getStatus().withContext(
str::stream() << "Failed to resolve view '" << involvedNs.ns());
}
auto&& underlyingNs = resolvedView.getValue().getNamespace();
// Attempt to acquire UUID of the underlying collection using lock free method.
auto uuid = catalog->lookupUUIDByNSS(opCtx, underlyingNs);
resolvedNamespaces[ns.coll()] = {
underlyingNs, resolvedView.getValue().getPipeline(), uuid};
// We parse the pipeline corresponding to the resolved view in case we must resolve
// other view namespaces that are also involved.
LiteParsedPipeline resolvedViewLitePipeline(resolvedView.getValue().getNamespace(),
resolvedView.getValue().getPipeline());
const auto& resolvedViewInvolvedNamespaces =
resolvedViewLitePipeline.getInvolvedNamespaces();
involvedNamespacesQueue.insert(involvedNamespacesQueue.end(),
resolvedViewInvolvedNamespaces.begin(),
resolvedViewInvolvedNamespaces.end());
return Status::OK();
};
// If the involved namespace is not in the same database as the aggregation, it must be
// from a $lookup/$graphLookup into a tenant migration donor's oplog view or from an
// $out/$merge to a collection in a different database.
if (involvedNs.db() != request.getNamespace().db()) {
if (involvedNs == NamespaceString::kTenantMigrationOplogView) {
// For tenant migrations, we perform an aggregation on 'config.transactions' but
// require a lookup stage involving a view on the 'local' database.
// If the involved namespace is 'local.system.tenantMigration.oplogView', resolve
// its view definition.
auto status = resolveViewDefinition(involvedNs);
if (!status.isOK()) {
return status;
}
} else {
// SERVER-51886: It is not correct to assume that we are reading from a collection
// because the collection targeted by $out/$merge on a given database can have the
// same name as a view on the source database. As such, we determine whether the
// collection name references a view on the aggregation request's database. Note
// that the inverse scenario (mistaking a view for a collection) is not an issue
// because $merge/$out cannot target a view.
auto nssToCheck = NamespaceString(request.getNamespace().db(), involvedNs.coll());
if (catalog->lookupView(opCtx, nssToCheck)) {
auto status = resolveViewDefinition(nssToCheck);
if (!status.isOK()) {
return status;
}
} else {
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}};
}
}
} else if (catalog->lookupCollectionByNamespace(opCtx, involvedNs)) {
// Attempt to acquire UUID of the collection using lock free method.
auto uuid = catalog->lookupUUIDByNSS(opCtx, involvedNs);
// If 'involvedNs' refers to a collection namespace, then we resolve it as an empty
// pipeline in order to read directly from the underlying collection.
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}, uuid};
} else if (catalog->lookupView(opCtx, involvedNs)) {
auto status = resolveViewDefinition(involvedNs);
if (!status.isOK()) {
return status;
}
} else {
// 'involvedNs' is neither a view nor a collection, so resolve it as an empty pipeline
// to treat it as reading from a non-existent collection.
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}};
}
}
return resolvedNamespaces;
}
/**
* Returns Status::OK if each view namespace in 'pipeline' has a default collator equivalent to
* 'collator'. Otherwise, returns ErrorCodes::OptionNotSupportedOnView.
*/
Status collatorCompatibleWithPipeline(OperationContext* opCtx,
StringData dbName,
const CollatorInterface* collator,
const LiteParsedPipeline& liteParsedPipeline) {
auto catalog = CollectionCatalog::get(opCtx);
for (auto&& potentialViewNs : liteParsedPipeline.getInvolvedNamespaces()) {
if (catalog->lookupCollectionByNamespace(opCtx, potentialViewNs)) {
continue;
}
auto view = catalog->lookupView(opCtx, potentialViewNs);
if (!view) {
continue;
}
if (!CollatorInterface::collatorsMatch(view->defaultCollator(), collator)) {
return {ErrorCodes::OptionNotSupportedOnView,
str::stream() << "Cannot override a view's default collation"
<< potentialViewNs.ns()};
}
}
return Status::OK();
}
boost::intrusive_ptr<ExpressionContext> makeExpressionContext(
OperationContext* opCtx,
const AggregateCommandRequest& request,
std::unique_ptr<CollatorInterface> collator,
boost::optional<UUID> uuid,
ExpressionContext::CollationMatchesDefault collationMatchesDefault) {
boost::intrusive_ptr<ExpressionContext> expCtx =
new ExpressionContext(opCtx,
request,
std::move(collator),
MongoProcessInterface::create(opCtx),
uassertStatusOK(resolveInvolvedNamespaces(opCtx, request)),
uuid,
CurOp::get(opCtx)->dbProfileLevel() > 0);
expCtx->tempDir = storageGlobalParams.dbpath + "/_tmp";
expCtx->collationMatchesDefault = collationMatchesDefault;
expCtx->forPerShardCursor = request.getPassthroughToShard().has_value();
expCtx->allowDiskUse = request.getAllowDiskUse().value_or(allowDiskUseByDefault.load());
if (opCtx->readOnly()) {
// Disallow disk use if in read-only mode.
expCtx->allowDiskUse = false;
}
// If the request explicitly specified NOT to use v2 resume tokens for change streams, set this
// on the expCtx. This can happen if a the request originated from 6.0 mongos, or in test mode.
if (request.getGenerateV2ResumeTokens().has_value()) {
// We only ever expect an explicit $_generateV2ResumeTokens to be false.
uassert(6528200, "Invalid request for v2 tokens", !request.getGenerateV2ResumeTokens());
expCtx->changeStreamTokenVersion = 1;
}
return expCtx;
}
/**
* Upconverts the read concern for a change stream aggregation, if necesssary.
*
* If there is no given read concern level on the given object, upgrades the level to 'majority' and
* waits for read concern. If a read concern level is already specified on the given read concern
* object, this method does nothing.
*/
void _adjustChangeStreamReadConcern(OperationContext* opCtx) {
repl::ReadConcernArgs& readConcernArgs = repl::ReadConcernArgs::get(opCtx);
// There is already a non-default read concern level set. Do nothing.
if (readConcernArgs.hasLevel() && !readConcernArgs.getProvenance().isImplicitDefault()) {
return;
}
// We upconvert an empty read concern to 'majority'.
{
// We must obtain the client lock to set the ReadConcernArgs on the operation
// context as it may be concurrently read by CurrentOp.
stdx::lock_guard<Client> lk(*opCtx->getClient());
readConcernArgs = repl::ReadConcernArgs(repl::ReadConcernLevel::kMajorityReadConcern);
// Change streams are allowed to use the speculative majority read mechanism, if
// the storage engine doesn't support majority reads directly.
if (!serverGlobalParams.enableMajorityReadConcern) {
readConcernArgs.setMajorityReadMechanism(
repl::ReadConcernArgs::MajorityReadMechanism::kSpeculative);
}
}
// Wait for read concern again since we changed the original read concern.
uassertStatusOK(waitForReadConcern(opCtx, readConcernArgs, StringData(), true));
setPrepareConflictBehaviorForReadConcern(
opCtx, readConcernArgs, PrepareConflictBehavior::kIgnoreConflicts);
}
/**
* If the aggregation 'request' contains an exchange specification, create a new pipeline for each
* consumer and put it into the resulting vector. Otherwise, return the original 'pipeline' as a
* single vector element.
*/
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> createExchangePipelinesIfNeeded(
OperationContext* opCtx,
boost::intrusive_ptr<ExpressionContext> expCtx,
const AggregateCommandRequest& request,
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
boost::optional<UUID> uuid) {
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> pipelines;
if (request.getExchange() && !expCtx->explain) {
boost::intrusive_ptr<Exchange> exchange =
new Exchange(request.getExchange().get(), std::move(pipeline));
for (size_t idx = 0; idx < exchange->getConsumers(); ++idx) {
// For every new pipeline we have create a new ExpressionContext as the context
// cannot be shared between threads. There is no synchronization for pieces of
// the execution machinery above the Exchange, so nothing above the Exchange can be
// shared between different exchange-producer cursors.
expCtx = makeExpressionContext(opCtx,
request,
expCtx->getCollator() ? expCtx->getCollator()->clone()
: nullptr,
uuid,
expCtx->collationMatchesDefault);
// Create a new pipeline for the consumer consisting of a single
// DocumentSourceExchange.
boost::intrusive_ptr<DocumentSource> consumer = new DocumentSourceExchange(
expCtx,
exchange,
idx,
// Assumes this is only called from the 'aggregate' or 'getMore' commands. The code
// which relies on this parameter does not distinguish/care about the difference so
// we simply always pass 'aggregate'.
expCtx->mongoProcessInterface->getResourceYielder("aggregate"_sd));
pipelines.emplace_back(Pipeline::create({consumer}, expCtx));
}
} else {
pipelines.emplace_back(std::move(pipeline));
}
return pipelines;
}
/**
* Creates additional pipelines if needed to serve the aggregation. This includes additional
* pipelines for exchange optimization and search commands that generate metadata. Returns
* a vector of all pipelines needed for the query, including the original one.
*
* Takes ownership of the original, passed in, pipeline.
*/
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> createAdditionalPipelinesIfNeeded(
OperationContext* opCtx,
boost::intrusive_ptr<ExpressionContext> expCtx,
const AggregateCommandRequest& request,
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
boost::optional<UUID> collUUID) {
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> pipelines;
// Exchange is not allowed to be specified if there is a $search stage.
if (auto metadataPipe = getSearchHelpers(opCtx->getServiceContext())
->generateMetadataPipelineForSearch(
opCtx, expCtx, request, pipeline.get(), collUUID)) {
pipelines.push_back(std::move(pipeline));
pipelines.push_back(std::move(metadataPipe));
} else {
// Takes ownership of 'pipeline'.
pipelines =
createExchangePipelinesIfNeeded(opCtx, expCtx, request, std::move(pipeline), collUUID);
}
return pipelines;
}
/**
* Performs validations related to API versioning and time-series stages.
* Throws UserAssertion if any of the validations fails
* - validation of API versioning on each stage on the pipeline
* - validation of API versioning on 'AggregateCommandRequest' request
* - validation of time-series related stages
*/
void performValidationChecks(const OperationContext* opCtx,
const AggregateCommandRequest& request,
const LiteParsedPipeline& liteParsedPipeline) {
liteParsedPipeline.validate(opCtx);
aggregation_request_helper::validateRequestForAPIVersion(opCtx, request);
}
std::vector<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> createLegacyExecutor(
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
const LiteParsedPipeline& liteParsedPipeline,
const NamespaceString& nss,
const MultipleCollectionAccessor& collections,
const AggregateCommandRequest& request,
CurOp* curOp,
const std::function<void(void)>& resetContextFn) {
const auto expCtx = pipeline->getContext();
// Check if the pipeline has a $geoNear stage, as it will be ripped away during the build query
// executor phase below (to be replaced with a $geoNearCursorStage later during the executor
// attach phase).
auto hasGeoNearStage = !pipeline->getSources().empty() &&
dynamic_cast<DocumentSourceGeoNear*>(pipeline->peekFront());
// Prepare a PlanExecutor to provide input into the pipeline, if needed.
auto attachExecutorCallback =
PipelineD::buildInnerQueryExecutor(collections, nss, &request, pipeline.get());
std::vector<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> execs;
if (canOptimizeAwayPipeline(pipeline.get(),
attachExecutorCallback.second.get(),
request,
hasGeoNearStage,
liteParsedPipeline.hasChangeStream())) {
// Mark that this query does not use DocumentSource.
curOp->debug().documentSourceUsed = false;
// This pipeline is currently empty, but once completed it will have only one source,
// which is a DocumentSourceCursor. Instead of creating a whole pipeline to do nothing
// more than forward the results of its cursor document source, we can use the
// PlanExecutor by itself. The resulting cursor will look like what the client would
// have gotten from find command.
execs.emplace_back(std::move(attachExecutorCallback.second));
} else {
// Mark that this query uses DocumentSource.
curOp->debug().documentSourceUsed = true;
getSearchHelpers(expCtx->opCtx->getServiceContext())
->injectSearchShardFiltererIfNeeded(pipeline.get());
// Complete creation of the initial $cursor stage, if needed.
PipelineD::attachInnerQueryExecutorToPipeline(collections,
attachExecutorCallback.first,
std::move(attachExecutorCallback.second),
pipeline.get());
auto pipelines = createAdditionalPipelinesIfNeeded(
expCtx->opCtx, expCtx, request, std::move(pipeline), expCtx->uuid);
for (auto&& pipelineIt : pipelines) {
// There are separate ExpressionContexts for each exchange pipeline, so make sure to
// pass the pipeline's ExpressionContext to the plan executor factory.
auto pipelineExpCtx = pipelineIt->getContext();
execs.emplace_back(
plan_executor_factory::make(std::move(pipelineExpCtx),
std::move(pipelineIt),
aggregation_request_helper::getResumableScanType(
request, liteParsedPipeline.hasChangeStream())));
}
// With the pipelines created, we can relinquish locks as they will manage the locks
// internally further on. We still need to keep the lock for an optimized away pipeline
// though, as we will be changing its lock policy to 'kLockExternally' (see details
// below), and in order to execute the initial getNext() call in 'handleCursorCommand',
// we need to hold the collection lock.
resetContextFn();
}
return execs;
}
} // namespace
Status runAggregate(OperationContext* opCtx,
const NamespaceString& nss,
AggregateCommandRequest& request,
const BSONObj& cmdObj,
const PrivilegeVector& privileges,
rpc::ReplyBuilderInterface* result) {
return runAggregate(opCtx, nss, request, {request}, cmdObj, privileges, result);
}
Status runAggregate(OperationContext* opCtx,
const NamespaceString& origNss,
AggregateCommandRequest& request,
const LiteParsedPipeline& liteParsedPipeline,
const BSONObj& cmdObj,
const PrivilegeVector& privileges,
rpc::ReplyBuilderInterface* result) {
// Perform some validations on the LiteParsedPipeline and request before continuing with the
// aggregation command.
performValidationChecks(opCtx, request, liteParsedPipeline);
// For operations on views, this will be the underlying namespace.
NamespaceString nss = request.getNamespace();
// Determine if this aggregation has foreign collections that the execution subsystem needs
// to be aware of.
std::vector<NamespaceStringOrUUID> secondaryExecNssList;
// Taking locks over multiple collections is not supported outside of $lookup pushdown.
if (feature_flags::gFeatureFlagSBELookupPushdown.isEnabledAndIgnoreFCV()) {
secondaryExecNssList = liteParsedPipeline.getForeignExecutionNamespaces();
}
// The collation to use for this aggregation. boost::optional to distinguish between the case
// where the collation has not yet been resolved, and where it has been resolved to nullptr.
boost::optional<std::unique_ptr<CollatorInterface>> collatorToUse;
ExpressionContext::CollationMatchesDefault collatorToUseMatchesDefault;
// The UUID of the collection for the execution namespace of this aggregation.
boost::optional<UUID> uuid;
// If emplaced, AutoGetCollectionForReadCommand will throw if the sharding version for this
// connection is out of date. If the namespace is a view, the lock will be released before
// re-running the expanded aggregation.
boost::optional<AutoGetCollectionForReadCommandMaybeLockFree> ctx;
MultipleCollectionAccessor collections;
auto initContext = [&](AutoGetCollectionViewMode m) -> void {
ctx.emplace(opCtx,
nss,
m,
Date_t::max(),
AutoStatsTracker::LogMode::kUpdateTopAndCurOp,
secondaryExecNssList);
collections = MultipleCollectionAccessor(opCtx,
&ctx->getCollection(),
ctx->getNss(),
ctx->isAnySecondaryNamespaceAViewOrSharded(),
secondaryExecNssList);
};
auto resetContext = [&]() -> void {
ctx.reset();
collections.clear();
};
std::vector<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> execs;
boost::intrusive_ptr<ExpressionContext> expCtx;
auto curOp = CurOp::get(opCtx);
auto catalog = CollectionCatalog::get(opCtx);
{
// If we are in a transaction, check whether the parsed pipeline supports being in
// a transaction and if the transaction's read concern is supported.
if (opCtx->inMultiDocumentTransaction()) {
liteParsedPipeline.assertSupportsMultiDocumentTransaction(request.getExplain());
liteParsedPipeline.assertSupportsReadConcern(opCtx, request.getExplain());
}
const auto& pipelineInvolvedNamespaces = liteParsedPipeline.getInvolvedNamespaces();
// If this is a collectionless aggregation, we won't create 'ctx' but will still need an
// AutoStatsTracker to record CurOp and Top entries.
boost::optional<AutoStatsTracker> statsTracker;
// If this is a change stream, perform special checks and change the execution namespace.
if (liteParsedPipeline.hasChangeStream()) {
uassert(4928900,
str::stream() << AggregateCommandRequest::kCollectionUUIDFieldName
<< " is not supported for a change stream",
!request.getCollectionUUID());
// Replace the execution namespace with that of the oplog.
nss = NamespaceString::kRsOplogNamespace;
// Upgrade and wait for read concern if necessary.
_adjustChangeStreamReadConcern(opCtx);
// Raise an error if 'origNss' is a view. We do not need to check this if we are opening
// a stream on an entire db or across the cluster.
const TenantDatabaseName origTenantDbName(boost::none, origNss.db());
if (!origNss.isCollectionlessAggregateNS()) {
auto view = catalog->lookupView(opCtx, origNss);
uassert(ErrorCodes::CommandNotSupportedOnView,
str::stream()
<< "Namespace " << origNss.ns() << " is a timeseries collection",
!view || !view->timeseries());
uassert(ErrorCodes::CommandNotSupportedOnView,
str::stream()
<< "Namespace " << origNss.ns() << " is a view, not a collection",
!view);
}
// If the user specified an explicit collation, adopt it; otherwise, use the simple
// collation. We do not inherit the collection's default collation or UUID, since
// the stream may be resuming from a point before the current UUID existed.
auto [collator, match] = PipelineD::resolveCollator(
opCtx, request.getCollation().get_value_or(BSONObj()), nullptr);
collatorToUse.emplace(std::move(collator));
collatorToUseMatchesDefault = match;
// Obtain collection locks on the execution namespace; that is, the oplog.
initContext(AutoGetCollectionViewMode::kViewsForbidden);
} else if (nss.isCollectionlessAggregateNS() && pipelineInvolvedNamespaces.empty()) {
uassert(4928901,
str::stream() << AggregateCommandRequest::kCollectionUUIDFieldName
<< " is not supported for a collectionless aggregation",
!request.getCollectionUUID());
// If this is a collectionless agg with no foreign namespaces, don't acquire any locks.
statsTracker.emplace(opCtx,
nss,
Top::LockType::NotLocked,
AutoStatsTracker::LogMode::kUpdateTopAndCurOp,
0);
auto [collator, match] = PipelineD::resolveCollator(
opCtx, request.getCollation().get_value_or(BSONObj()), nullptr);
collatorToUse.emplace(std::move(collator));
collatorToUseMatchesDefault = match;
tassert(6235101,
"A collection-less aggregate should not take any locks",
ctx == boost::none);
} else {
// This is a regular aggregation. Lock the collection or view.
initContext(AutoGetCollectionViewMode::kViewsPermitted);
auto [collator, match] =
PipelineD::resolveCollator(opCtx,
request.getCollation().get_value_or(BSONObj()),
collections.getMainCollection());
collatorToUse.emplace(std::move(collator));
collatorToUseMatchesDefault = match;
if (collections.hasMainCollection()) {
uuid = collections.getMainCollection()->uuid();
}
}
// If this is a view, resolve it by finding the underlying collection and stitching view
// pipelines and this request's pipeline together. We then release our locks before
// recursively calling runAggregate(), which will re-acquire locks on the underlying
// collection. (The lock must be released because recursively acquiring locks on the
// database will prohibit yielding.)
if (ctx && ctx->getView() && !liteParsedPipeline.startsWithCollStats()) {
invariant(nss != NamespaceString::kRsOplogNamespace);
invariant(!nss.isCollectionlessAggregateNS());
checkCollectionUUIDMismatch(
opCtx, nss, collections.getMainCollection(), request.getCollectionUUID());
uassert(ErrorCodes::CommandNotSupportedOnView,
"mapReduce on a view is not supported",
!request.getIsMapReduceCommand());
// Check that the default collation of 'view' is compatible with the operation's
// collation. The check is skipped if the request did not specify a collation.
if (!request.getCollation().get_value_or(BSONObj()).isEmpty()) {
invariant(collatorToUse); // Should already be resolved at this point.
if (!CollatorInterface::collatorsMatch(ctx->getView()->defaultCollator(),
collatorToUse->get()) &&
!ctx->getView()->timeseries()) {
return {ErrorCodes::OptionNotSupportedOnView,
"Cannot override a view's default collation"};
}
}
// Queries on timeseries views may specify non-default collation whereas queries
// on all other types of views must match the default collator (the collation use
// to originally create that collections). Thus in the case of operations on TS
// views, we use the request's collation.
auto timeSeriesCollator =
ctx->getView()->timeseries() ? request.getCollation() : boost::none;
auto resolvedView = uassertStatusOK(
view_catalog_helpers::resolveView(opCtx, catalog, nss, timeSeriesCollator));
// With the view & collation resolved, we can relinquish locks.
resetContext();
// Set this operation's shard version for the underlying collection to unsharded.
// This is prerequisite for future shard versioning checks.
ScopedSetShardRole scopedSetShardRole(opCtx,
resolvedView.getNamespace(),
ChunkVersion::UNSHARDED() /* shardVersion */,
boost::none /* databaseVersion */);
uassert(std::move(resolvedView),
"Explain of a resolved view must be executed by mongos",
!ShardingState::get(opCtx)->enabled() || !request.getExplain());
// Parse the resolved view into a new aggregation request.
auto newRequest = resolvedView.asExpandedViewAggregation(request);
auto newCmd = aggregation_request_helper::serializeToCommandObj(newRequest);
auto status{Status::OK()};
try {
status = runAggregate(opCtx, origNss, newRequest, newCmd, privileges, result);
} catch (const ExceptionForCat<ErrorCategory::StaleShardVersionError>& ex) {
// Since we expect the view to be UNSHARDED, if we reached to this point there are
// two possibilities:
// 1. The shard doesn't know what its shard version/state is and needs to recover
// it (in which case we throw so that the shard can run recovery)
// 2. The collection references by the view is actually SHARDED, in which case the
// router must execute it
if (const auto staleInfo{ex.extraInfo<StaleConfigInfo>()}) {
uassert(std::move(resolvedView),
"Resolved views on sharded collections must be executed by mongos",
!staleInfo->getVersionWanted());
}
throw;
}
{
// Set the namespace of the curop back to the view namespace so ctx records
// stats on this view namespace on destruction.
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setNS_inlock(nss.ns());
}
return status;
}
// If collectionUUID was provided, verify the collection exists and has the expected UUID.
checkCollectionUUIDMismatch(
opCtx, nss, collections.getMainCollection(), request.getCollectionUUID());
invariant(collatorToUse);
expCtx = makeExpressionContext(
opCtx, request, std::move(*collatorToUse), uuid, collatorToUseMatchesDefault);
expCtx->startExpressionCounters();
auto pipeline = Pipeline::parse(request.getPipeline(), expCtx);
expCtx->stopExpressionCounters();
if (!request.getAllowDiskUse().value_or(true)) {
allowDiskUseFalseCounter.increment();
}
// Check that the view's collation matches the collation of any views involved in the
// pipeline.
if (!pipelineInvolvedNamespaces.empty()) {
auto pipelineCollationStatus = collatorCompatibleWithPipeline(
opCtx, nss.db(), expCtx->getCollator(), liteParsedPipeline);
if (!pipelineCollationStatus.isOK()) {
return pipelineCollationStatus;
}
}
// If the aggregate command supports encrypted collections, do rewrites of the pipeline to
// support querying against encrypted fields.
if (shouldDoFLERewrite(request)) {
// After this rewriting, the encryption info does not need to be kept around.
pipeline = processFLEPipelineD(
opCtx, nss, request.getEncryptionInformation().get(), std::move(pipeline));
request.setEncryptionInformation(boost::none);
}
pipeline->optimizePipeline();
constexpr bool alreadyOptimized = true;
pipeline->validateCommon(alreadyOptimized);
if (feature_flags::gfeatureFlagCommonQueryFramework.isEnabled(
serverGlobalParams.featureCompatibility) &&
internalQueryEnableCascadesOptimizer.load()) {
uassert(6624344,
"Exchanging is not supported in the Cascades optimizer",
!request.getExchange().has_value());
auto timeBegin = Date_t::now();
execs.emplace_back(getSBEExecutorViaCascadesOptimizer(
opCtx, expCtx, nss, collections.getMainCollection(), *pipeline));
auto elapsed =
(Date_t::now().toMillisSinceEpoch() - timeBegin.toMillisSinceEpoch()) / 1000.0;
std::cerr << "Optimization took: " << elapsed << " s.\n";
} else {
execs = createLegacyExecutor(std::move(pipeline),
liteParsedPipeline,
nss,
collections,
request,
curOp,
resetContext);
}
tassert(6624353, "No executors", !execs.empty());
{
auto planSummary = execs[0]->getPlanExplainer().getPlanSummary();
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setPlanSummary_inlock(std::move(planSummary));
}
}
// Having released the collection lock, we can now create a cursor that returns results from the
// pipeline. This cursor owns no collection state, and thus we register it with the global
// cursor manager. The global cursor manager does not deliver invalidations or kill
// notifications; the underlying PlanExecutor(s) used by the pipeline will be receiving
// invalidations and kill notifications themselves, not the cursor we create here.
std::vector<ClientCursorPin> pins;
std::vector<ClientCursor*> cursors;
ScopeGuard cursorFreer([&] {
for (auto& p : pins) {
p.deleteUnderlying();
}
});
for (auto&& exec : execs) {
ClientCursorParams cursorParams(
std::move(exec),
origNss,
AuthorizationSession::get(opCtx->getClient())->getAuthenticatedUserNames(),
APIParameters::get(opCtx),
opCtx->getWriteConcern(),
repl::ReadConcernArgs::get(opCtx),
ReadPreferenceSetting::get(opCtx),
cmdObj,
privileges);
cursorParams.setTailableMode(expCtx->tailableMode);
auto pin = CursorManager::get(opCtx)->registerCursor(opCtx, std::move(cursorParams));
pin->incNBatches();
cursors.emplace_back(pin.getCursor());
pins.emplace_back(std::move(pin));
}
// Report usage statistics for each stage in the pipeline.
liteParsedPipeline.tickGlobalStageCounters();
// If both explain and cursor are specified, explain wins.
if (expCtx->explain) {
auto explainExecutor = pins[0]->getExecutor();
auto bodyBuilder = result->getBodyBuilder();
if (auto pipelineExec = dynamic_cast<PlanExecutorPipeline*>(explainExecutor)) {
Explain::explainPipeline(
pipelineExec, true /* executePipeline */, *(expCtx->explain), cmdObj, &bodyBuilder);
} else {
invariant(explainExecutor->getOpCtx() == opCtx);
// The explainStages() function for a non-pipeline executor may need to execute the plan
// to collect statistics. If the PlanExecutor uses kLockExternally policy, the
// appropriate collection lock must be already held. Make sure it has not been released
// yet.
invariant(ctx);
Explain::explainStages(explainExecutor,
ctx->getCollection(),
*(expCtx->explain),
BSON("optimizedPipeline" << true),
cmdObj,
&bodyBuilder);
}
} else {
// Cursor must be specified, if explain is not.
const bool keepCursor = handleCursorCommand(
opCtx, expCtx, origNss, std::move(cursors), request, cmdObj, result);
if (keepCursor) {
cursorFreer.dismiss();
}
const auto& planExplainer = pins[0].getCursor()->getExecutor()->getPlanExplainer();
PlanSummaryStats stats;
planExplainer.getSummaryStats(&stats);
curOp->debug().setPlanSummaryMetrics(stats);
curOp->debug().nreturned = stats.nReturned;
// For an optimized away pipeline, signal the cache that a query operation has completed.
// For normal pipelines this is done in DocumentSourceCursor.
if (ctx) {
// Due to yielding, the collection pointers saved in MultipleCollectionAccessor might
// have become invalid. We will need to refresh them here.
collections = MultipleCollectionAccessor(opCtx,
&ctx->getCollection(),
ctx->getNss(),
ctx->isAnySecondaryNamespaceAViewOrSharded(),
secondaryExecNssList);
if (const auto& coll = ctx->getCollection()) {
CollectionQueryInfo::get(coll).notifyOfQuery(opCtx, coll, stats);
}
// For SBE pushed down pipelines, we may need to report stats saved for secondary
// collections separately.
for (const auto& [secondaryNss, coll] : collections.getSecondaryCollections()) {
if (coll) {
PlanSummaryStats secondaryStats;
planExplainer.getSecondarySummaryStats(secondaryNss.toString(),
&secondaryStats);
CollectionQueryInfo::get(coll).notifyOfQuery(opCtx, coll, secondaryStats);
}
}
}
}
// The aggregation pipeline may change the namespace of the curop and we need to set it back to
// the original namespace to correctly report command stats. One example when the namespace can
// be changed is when the pipeline contains an $out stage, which executes an internal command to
// create a temp collection, changing the curop namespace to the name of this temp collection.
{
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setNS_inlock(origNss.ns());
}
return Status::OK();
}
} // namespace mongo
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